The Jelly Calculator
Certo's whole promise is proportion: so much juice, so much sugar, so much pectin, one minute's hard boil. Pick a recipe and say how much fruit or juice you have — the calculator keeps the book's ratios exactly.
“Mother Nature's Jell Maker” — the 1922 leaflet that promised no more boiling the flavour away, with an exact recipe for every fruit.
Certo's whole promise is proportion: so much juice, so much sugar, so much pectin, one minute's hard boil. Pick a recipe and say how much fruit or juice you have — the calculator keeps the book's ratios exactly.